Injectable physiological monitoring system

ABSTRACT

An injectable device for use in a subcutaneous physiological monitoring of a patient includes a body, a plurality of sensors, and a monitoring unit. The plurality of sensors provide an indication of at least one physiological event of a patient, wherein the plurality of sensors includes two or more electrodes in contact with tissue of the patient. The monitoring unit is located within the body and is coupled to the plurality of sensors and configured to monitor a physiologic signal of the patient using the electrodes, wherein the physiologic signal includes an impedance signal related to hydration of tissue of the patient and wherein the monitoring unit is further configured to, based at least in part on the impedance signal measured from the patient, detect an impending cardiac decompensation of the patient.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a Continuing application of U.S. application Ser.No. 12/209,479, filed on 12 Sep. 2008, which claims the benefit under 35USC 119(e) of U.S. Provisional Application Nos. 60/972,329, 60/972,336,60/972,354 and 60/972,537, all filed Sep. 14, 2007, and 61/055,666 filedMay 23, 2008; the full disclosures of which are incorporated herein byreference in their entirety. A claim of priority to all, to the extentappropriate, is made.

BACKGROUND OF THE INVENTION

Field of the Invention

This invention relates generally to systems and methods for remotepatient monitoring, and more particularly to an injectable physiologicalmonitoring system for decompensation prediction of a heart failurepatient.

Frequent monitoring of patients permits the patients' physician todetect worsening symptoms as they begin to occur, rather than waitinguntil a critical condition has been reached. As such, home monitoring ofpatients with chronic conditions is becoming increasingly popular in thehealth care industry for the array of benefits it has the potential toprovide. Potential benefits of home monitoring are numerous and include:better tracking and management of chronic disease conditions, earlierdetection of changes in the patient condition, and reduction of overallhealth care expenses associated with long term disease management. Thehome monitoring of a number of diverse “chronic diseases” is ofinterest, where such diseases include diabetes, dietary disorders suchas anorexia and obesity, anxiety, depression, epilepsy respiratorydiseases, AIDS and other chronic viral conditions, conditions associatedwith the long term use of immunosuppressant's, e.g. in transplantpatients, asthma, chronic hypertension, chronic use of anticoagulants,and the like.

Of particular interest in the home monitoring sector of the health careindustry is the remote monitoring of patients with heart failure (HF),also known as congestive heart failure. HF is a syndrome in which theheart is unable to efficiently pump blood to the vital organs. Mostinstances of HF occur because of a decreased myocardial capacity tocontract (systolic dysfunction). However, HF can also result when anincreased pressure-stroke-volume load is imposed on the heart, such aswhen the heart is unable to expand sufficiently during diastole toaccommodate the ventricular volume, causing an increased pressure load(diasystolic dysfunction).

In either case, HF is characterized by diminished cardiac output and/ordamming back of blood in the venous system. In HF, there is a shift inthe cardiac function curve and an increase in blood volume caused inpart by fluid retention by the kidneys. Indeed, many of the significantmorphologic changes encountered in HF are distant from the heart and areproduced by the hypoxic and congestive effects of the failingcirculation upon other organs and tissues. One of the major symptoms ofHF is edema, which has been defined as the excessive accumulation ofinterstitial fluid, either localized or generalized.

HF is the most common indication for hospitalization among adults over65 years of age, and the rate of admission for this condition hasincreased progressively over the past two decades. It has been estimatedthat HF affects more than 3 million patients in the U.S. (O'Connell, J.B. et al., J. Heart Lung Transpl., 13(4):S107-112 (1993)).

In the conventional management of HF patents, where help is sought onlyin crisis, a cycle occurs where patients fail to recognize earlysymptoms and do not seek timely help from their care-givers, leading toemergency department admissions (Miller, P. Z., Home monitoring forcongestive heart failure patients, Caring Magazine, 53-54 (August1995)).

Recently, a prospective, randomized trial of 282 patients was conductedto assess the effect of the intervention on the rate of admission,quality of life, and cost of medical care. In this study, anurse-directed, multi-disciplinary intervention (which consisted ofcomprehensive education of the patient and family, diet, social-serviceconsultation and planning, review of medications, and intensiveassessment of patient condition and follow-up) resulted in fewerreadmissions than the conventional treatment group and a concomitantoverall decrease in the cost of care (Rich, M. W. et al., New Engl. J.Med., 333:1190-95 (1995)).

Similarly, comprehensive discharge planning and a home follow-up programwas shown to decrease the number of readmissions and total hospitalcharges in an elderly population (Naylor, M. et al., Amer. CollegePhysicians, 120:999-1006 (1994)). Therefore, home monitoring is ofparticular interest in the HF management segment of the health careindustry.

Another area in which home-monitoring is of particular interest is inthe remote monitoring of a patient parameter that provides informationon the titration of a drug, particularly with drugs that have aconsequential effect following administration, such as insulin,anticoagulants, ACE inhibitors, beta-blockers, diuretics and the like.

Although a number of different home monitoring systems have beendeveloped, there is continued interest in the development of newmonitoring systems. Of particular interest would be the development of asystem that provides for improved patient compliance, ease of use, etc.Of more particular interest would be the development of such a systemthat is particularly suited for use in the remote monitoring of patientssuffering from HF.

Subcutaneous implantation of sensors has been achieved with an insertionand tunneling tool. The tunneling tool includes a stylet and a peel-awaysheath. The tunneling tool is inserted into an incision and the styletis withdrawn once the tunneling tool reaches a desired position. Anelectrode segment is inserted into the subcutaneous tunnel and thepeel-away sheath is removed. In another delivery device, a pointed tipis inserted through the skin and a plunger is actuated to drive thesensor to its desired location.

In other delivery systems, an implant trocar includes a cannula forpuncturing the skin and an obturator for delivering the implant. Aspring element received within the cannula prevents the sensor fromfalling out during the implant process. Another sensor delivery deviceincludes an injector that has a tubular body divided into two adjacentsegments with a hollow interior bore. A pair of laterally adjacent tinesextend longitudinally from the first segment to the distal end of thetubular body. A plunger rod has an exterior diameter just slightlylarger than the interior diameter of the tubular body. With the secondsegment inserted beneath the skin, the push rod is advancedlongitudinally through the tubular body, thereby pushing the sensorthrough the bore. As the implant and rod pass through the secondsegment, the tines are forced radially away from each other, therebydilating or expanding the incision, and facilitating implant. Theinstrument is removed from the incision following implantation.

For the above and other reasons, it would be desirable to provide anon-surgical instrument and method for subcutaneous implantation ofsensors and solid materials that preferably does not require an incisionpreparatory to instrument insertion. It would also be desirable toprovide an improved home monitoring of patients with chronic conditionsand improved percutaneous sensor delivery devices.

BRIEF SUMMARY OF THE INVENTION

In a first aspect, embodiments of the present invention provide a systemfor decompensation prediction of a heart failure patient. The systemcomprises one or more injectable detecting systems having a plurality ofsensors that provide an indication of at least one physiological eventof a patient, a wireless communication device coupled to the one or moreinjectable detecting systems and configured to transfer patient datadirectly or indirectly from the one or more injectable detecting systemsto a remote monitoring system, and a remote monitoring system coupled tothe wireless communication device, the remote monitoring system usingprocessed data to determine heart failure status and predict impendingdecompensation of the patient.

In another aspect, embodiments of the present invention provide a systemfor decompensation prediction of a heart failure patient. The systemcomprises one or more injectable detecting systems having a plurality ofsensors that provide an indication of at least one physiological eventof a patient, the one or more injectable detecting systems beinginserted below the skin of the patient, the one or more injectabledetecting systems being injected below the skin of the patient by gun orsyringe injection, a wireless communication device coupled to the one ormore injectable detecting systems and configured to transfer patientdata directly or indirectly from the one or more injectable detectingsystems to a remote monitoring system, and a remote monitoring systemcoupled to the wireless communication device, the remote monitoringsystem using processed data to determine heart failure status andpredict impending decompensation of the patient.

In another aspect, embodiments of the present invention provide a methodfor decompensation prediction of a heart failure patient. The methodcomprising injecting subcutaneously one or more injectable detectingsystems having a plurality of sensors that provide an indication of atleast one physiological event of a patient, wirelessly transferringpatient data directly or indirectly from the one or more injectabledetecting systems to a remote monitoring system via a wirelesscommunication device coupled to the one or more injectable detectingsystems, and processing the data using the remote monitoring system todetermine heart failure status and predict impending decompensation ofthe patient.

In many embodiments, the one or more injectable detecting systems areinserted below the skin of the patient by at least one of, catheterdelivery, blunt tunneling and needle insertion.

In many embodiments, the systems and methods further comprise an imagingsystem to assist in guiding the injectable detecting system to a desiredlocation.

In many embodiments, each of a sensor is selected from at least one of,bioimpedance, heart rate, heart rhythm, HRV, HRT, heart sounds,respiratory sounds, respiratory rate and respiratory rate variability,blood pressure, activity, posture, wake/sleep, orthopnea, temperature,heat flux and an accelerometer.

In many embodiments, each of a sensor is an activity sensors selectedfrom at least one of, ball switch, accelerometer, minute ventilation,HR, bioimpedance noise, skin temperature/heat flux, BP, muscle noise andposture.

In many embodiments, the injectable detecting systems include a powersource, a memory, logic resources and an antenna. In many embodimentsthe power source is a rechargeable battery transcutaneously with anexternal unit.

In many embodiments, at least a portion of the injectable detectingsystems have a drug eluting coating.

In many embodiments, the one or more injectable detecting systems areanchored in the patient by at least one of, barbs, anchors, tissueadhesion pads, suture loops, shape of device, self-expanding metalstructure, wherein self-expanding metal structure is made of Nitinol.

In another aspect, embodiments of the present invention provide andinjection system for injecting one or more injectable physiologicalmonitoring systems for use in physiological monitoring of a patient. Thesystem includes a body capable of holding one or more injectablephysiological monitoring systems, the body having a proximal end anddistal end, wherein the distal end is shaped to penetrate tissue, a apusher configured to engage the one or more injectable physiologicalmonitoring systems within the body and a movable handle coupled to apusher configured to distally advance the one or more injectablephysiological monitoring systems through the body.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating one embodiment of a patientmonitoring system of the present invention.

FIG. 2(a) illustrates one embodiment of an injectable detecting systemof the present invention that is injectable and includes multiplesensors, power and communication and a communication antenna.

FIG. 2(b) illustrates the insertion of the device of FIG. 2(a) into aninjector.

FIG. 2(c) illustrates the device of FIG. 2(a) in the injector and readyto be introduced into the patient.

FIG. 2(d) illustrates the implanted sensor device of FIG. 2(a).

FIG. 2(e) illustrates the implanted sensor device of FIG. 2(a) as itflexes from a rigid state in the body.

FIG. 2(f) illustrates a patient laying on top of a matt that has coils,where downloading of patient data and recharging can occur via the mattor also through an adherent patch or wearable device by the patient.

FIG. 2(g) illustrates the patient laying on top of the matt from FIG.2(f) and the downloading of data from the sensors to the matt.

FIG. 2(h) is a close up view of FIG. 2(g) showing the downloading ofdata from the sensors to the matt, and then transfer of the data fromthe matt to a modem.

FIG. 2(i) illustrates a patient with an implanted device, such as apacing device, and the implanted device of FIG. 2(a) in communicationwith the implanted device.

FIG. 3 illustrates one embodiment of an energy management device that iscoupled to the plurality of sensors of FIG. 1.

FIG. 4 illustrates one embodiment of present invention illustratinglogic resources configured to receive data from the sensors and/or theprocessed patient for monitoring purposes, analysis and/or predictionpurposes.

FIG. 5 illustrates an embodiment of the patient monitoring system of thepresent invention with a memory management device.

FIG. 6 illustrates an embodiment of the patient monitoring system of thepresent invention with an external device coupled to the sensors.

FIG. 7 illustrates an embodiment of the patient monitoring system of thepresent invention with a notification device.

FIG. 8 is a block diagram illustrating an embodiment of the presentinvention with sensor leads that convey signals from the sensors to amonitoring unit at the detecting system, or through a wirelesscommunication device to a remote monitoring system.

FIG. 9 is a block diagram illustrating an embodiment of the presentinvention with a control unit at the detecting system and/or the remotemonitoring system.

FIG. 10 is a block diagram illustrating an embodiment of the presentinvention where a control unit encodes patient data and transmits it toa wireless network storage unit at the remote monitoring system.

FIG. 11 is a block diagram illustrating one embodiment of an internalstructure of a main data collection station at the remote monitoringsystem of the present invention.

FIG. 12 is a flow chart illustrating an embodiment of the presentinvention with operation steps performed by the system of the presentinvention in transmitting information to the main data collectionstation.

FIG. 13 shows one embodiment of an injection system for use withmultiple injectable detecting systems.

FIG. 14 shows one embodiment of an injection system that includes abevel needle shaped to receive the injectable detecting system.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to a heart failure patient managementsystem consisting of one or more subcutaneously injectable physiologicalmonitoring systems inserted below the patient's skin. The systemcontinuously monitors physiological parameters, communicates wirelesslywith a remote center, and provides alerts when necessary. A variety ofdelivery devices and methods are also disclosed.

The system monitors physiological parameters and uses a proprietaryalgorithm to determine heart failure status and predict impendingdecompensation. The injectable system communicates with a remote center,preferably via an intermediate device in the patient's home. In someembodiments, the remote center receives the data and applies theprediction algorithm. When a flag is raised, the center may communicatewith the patient, hospital, nurse, and/or physician to allow fortherapeutic intervention to prevent decompensation.

The injectable system may be inserted with one of the followingtechniques: catheter delivery, blunt tunneling (with either a separatetunneling tool or a wire-stiffened lead), and insertion with a needle.The injectable system may be injected with a gun or syringe-like device.The injectable system may be flexible, and may be implanted with astiffening wire or stylet.

The injectable system may be implanted in a non-sterile, non-surgicalsetting. Implantation may occur with or without local anesthesia, andwith or without imaging assistance.

The system may consist of an implantable component and an externalcomponent. In such an embodiment, the injected component, with orwithout physiological sensing electrodes, would be used to anchor anexternal electronics unit. The anchoring mechanism may be magnetic ormechanical.

The injectable system may contain one of the following features tofacilitate subsequent extraction: an isodiametric profile, a breakawayanchor, a bioabsorbable material, coatings to limit tissue in-growth,and an electrically activated or fusable anchor. The injectable systemmay be modular, containing multiple connected components, a subset ofwhich is easily extractable.

While the present invention is intended for heart failure patientmonitoring, the system may be applicable to any human application inwhich wireless physiological monitoring and prediction is required.

In one embodiment, illustrated in FIG. 1, the present invention is asystem that delivers a percutaneous sensing device for remote patientmonitoring. The remote monitoring tracks the patient's physiologicalstatus, detects and predicts negative physiological events. In oneembodiment, the implanted sensing device includes a plurality of sensorsthat are used in combination to enhance detection and predictioncapabilities as more fully explained below.

Referring again to FIG. 1, in one embodiment, the system 10 includes aninjectable detecting system 12 that includes a plurality of sensors 14and/or electrodes, that provide an indication of at least onephysiological event of a patient. The injectable detecting system 12 isinserted subcutaneously. In one embodiment the injectable detectingsystem 12 is inserted in the patient's thorax. The system 10 alsoincludes a wireless communication device 16, coupled to the plurality ofsensors 14. The wireless communication device transfers patient datadirectly or indirectly from the plurality of sensors 14 to a remotemonitoring system 18. The remote monitoring system 18 uses data from thesensors to determine the patient's status. The system 10 cancontinuously, or non-continuously, monitor the patient, alerts areprovided as necessary and medical intervention is provided whenrequired. In one embodiment, the wireless communication device 16 is awireless local area network for receiving data from the plurality ofsensors.

The sensors 14 are subcutaneously inserted with the injectable detectingsystem 12 that is catheter based, blunt tunneling (with either aseparate tunneling tool or a wire-stiffened lead), needle insertion gunor syringe-like injection. The injectable detecting system 12 can beflexible, and be used with a stiffening wire, stylet, catheter orguidewire. The injectable detecting system 12 can include any of thefollowing to assist in subsequent extraction: (i) an isodiametricprofile, (ii) a breakaway anchor, (iii) a bioabsorbable material, (iv)coatings to limit tissue in-growth, (v) an electrically activated orfusable anchor, and the like. The injectable detecting system 12 can bemodular, containing multiple connected components, a subset of which iseasily extractable.

The injectable detecting system 12 can be inserted in the patient in anon-sterile or sterile setting, non-surgical setting or surgicalsetting, implanted with our without anesthesia and implanted with orwithout imaging assistance from an imaging system. The injectabledetecting system 12 can be anchored in the patient by a variety of meansincluding but not limited to, barbs, anchors, tissue adhesion pads,suture loops, with sensor shapes that conform to adjacent tissue anatomyor provide pressure against the adjacent tissue, with the use ofself-expanding materials such as a nitinol anchor and the like.

FIG. 2(a) shows one embodiment of the injectable detecting system 12with sensors 14 that is introduced below the skin surface. The deviceincludes power and communication elements 32, and a communicationantenna 34. The antenna may be a self expanding antenna expandable froma first compressed shape to a second expanded shape, such as disclosedin U.S. Provisional Application No. 61/084,567, filed Jul. 29, 2008entitled “Communication-Anchor Loop For Injectable Device”, the fulldisclosure of which is incorporated herein by reference. FIG. 2(b)illustrates the injectable detecting system 12 being loaded into aninjector 36 having a needle end 38. FIG. 2(c) shows the injectabledetecting system 12 being introduced subcutaneously into a patient 40.FIG. 2(d) shows the injectable detecting system 12 being implantedsubcutaneously from the injector 36. In FIG. 2(e), the injector 36 isremoved and the injectable detecting system 12 flexes from a rigidconfiguration.

In one embodiment, illustrated in FIGS. 2(f) and 2(g), recharging coils42 are placed in a mat 44 on the patient's bed, such as under a mattresspad. Recharging of the sensors/battery and data transfer can occurduring sleep of the patient. The rechargeable batteries can betranscutaneously charged with an external unit other than the mat. FIG.2(g) shows downloading from the sensors and data transfer during sleepof the patient. In FIG. 2(h), the injectable detecting system 12downloads data to the mat and a modem is used from data transfer. InFIG. 2(i), an implantable device 50, such as a pacing devicecommunicates with the injectable detecting system 12 of FIG. 2(a).

In one embodiment, the wireless communication device 16 is configured toreceive instructional data from the remote monitoring system andcommunicate instructions to the injectable detecting system.

As illustrated in FIG. 3, an energy management device 19 is coupled tothe plurality of sensors. In one embodiment, the energy managementdevice 19 is part of the detecting system. In various embodiments, theenergy management device 19 performs one or more of, modulate drivelevels per sensed signal of a sensor 14, modulate a clock speed tooptimize energy, watch cell voltage drop - unload cell, coulomb-meter orother battery monitor, sensor dropoff at an end of life of a batterycoupled to a sensor, battery end of life dropoff to transfer data,elective replacement indicator, call center notification, sensingwindows by the sensors 14 based on a monitored physiological parameterand sensing rate control.

In one embodiment, the energy management device 19 is configured tomanage energy by at least one of, a thermo-electric unit, kinetics, fuelcell, nuclear power, a micro-battery and with a rechargeable device.

The system 10 is configured to automatically detect events. The system10 automatically detects events by at least one of, high noise states,physiological quietness, sensor continuity and compliance. In responseto a detected physiological event, patient states are identified whendata collection is inappropriate. In response to a detectedphysiological event, patient states are identified when data collectionis desirable. Patient states include, physiological quietness, rest,relaxation, agitation, movement, lack of movement and a patient's higherlevel of patient activity.

The system uses an intelligent combination of sensors to enhancedetection and prediction capabilities, as more fully discloses in U.S.patent application Ser. Nos. 60/972,537 filed Sep. 14, 2008 and61/055,666 filed May 23, 2008, both titled “Adherent Device withMultiple Physiological Sensors”, incorporated herein by reference, andas more fully explained below.

In one embodiment, the injectable detecting system 12 communicates withthe remote monitoring system 18 periodically or in response to a triggerevent. The trigger event can include but is not limited to at least oneof, time of day, if a memory is full, if an action is patient initiated,if an action is initiated from the remote monitoring system, adiagnostic event of the monitoring system, an alarm trigger, amechanical trigger, and the like.

The injectable detecting system 12 can continuously, ornon-continuously, monitor the patient, alerts are provided as necessaryand medical intervention is provided when required. In one embodiment,the wireless communication device 16 is a wireless local area networkfor receiving data from the plurality of sensors in the injectabledetecting system.

A processor 20 is coupled to the plurality of sensors 14 in theinjectable detecting system 12. The processor 20 receives data from theplurality of sensors 14 and creates processed patient data. In oneembodiment, the processor 20 is at the remote monitoring system 18. Inanother embodiment, the processor 20 is at the detecting system 12. Theprocessor 20 can be integral with a monitoring unit 22 that is part ofthe injectable detecting system 12 or part of the remote monitoringsystem 18.

The processor 20 has program instructions for evaluating values receivedfrom the sensors 14 with respect to acceptable physiological ranges foreach value received by the processor 20 and determine variances. Theprocessor 20 can receive and store a sensed measured parameter from thesensors 14, compare the sensed measured value with a predeterminedtarget value, determine a variance, accept and store a new predeterminedtarget value and also store a series of questions from the remotemonitoring system 18.

As illustrated in FIG. 4, logic resources 24 are provided that take thedata from the sensors 14, and/or the processed patient data from theprocessor 20, to predict an impending decompensation. The logicresources 24 can be at the remote monitoring system 18 or at thedetecting system 12, such as in the monitoring unit 22.

In one embodiment, a memory management device 25 is provided asillustrated in FIG. 5. In various embodiments, the memory managementdevice 25 performs one or more of data compression, prioritizing ofsensing by a sensor 14, monitoring all or some of sensor data by all ora portion of the sensors 14, sensing by the sensors 14 in real time,noise blanking to provide that sensor data is not stored if a selectednoise level is determined, low-power of battery caching and decimationof old sensor data.

The injectable detecting system 12 can provide a variety of differentfunctions, including but not limited to, initiation, programming,measuring, storing, analyzing, communicating, predicting, and displayingof a physiological event of the patient. The injectable detecting system12 can be sealed, such as housed in a hermetically sealed package. Inone embodiment, at least a portion of the sealed packages include apower source, a memory, logic resources and a wireless communicationdevice. In one embodiment, an antenna is included that is exterior tothe sealed package of the injectable detecting system 12. In oneembodiment, the sensors 14 include, flex circuits, thin film resistors,organic transistors and the like. The sensors 14 can include ceramics,titanium PEEK, along with a silicon, PU or other insulative adherentsealant, to enclose the electronics. Additionally, the injectabledetecting system 12 can include drug eluting coatings, including but notlimited to, an antibiotic, anti-inflammatory agent and the like.

A wide variety of different sensors 14 can be utilized, including butnot limited to, bioimpedance, heart rate, heart rhythm, HRV, HRT, heartsounds, respiration rate, respiration rate variability, respiratorysounds, SpO₂, blood pressure, activity, posture, wake/sleep, orthopnea,temperature, heat flux, an accelerometer. glucose sensor, other chemicalsensors associated with cardiac conditions, and the like. A varietyactivity sensors can be utilized, including but not limited to a, ballswitch, accelerometer, minute ventilation, HR, bioimpedance noise, skintemperature/heat flux, BP, muscle noise, posture and the like.

The output of the sensors 14 can have multiple features to enhancephysiological sensing performance. These multiple features have multiplesensing vectors that can include redundant vectors. The sensors 14 caninclude current delivery electrodes and sensing electrodes. Size andshape of current delivery electrodes, and the sensing electrodes, can beoptimized to maximize sensing performance. The system 10 can beconfigured to determine an optimal sensing configuration andelectronically reposition at least a portion of a sensing vector of asensing electrode. The multiple features enhance the system's 10 abilityto determine an optimal sensing configuration and electronicallyreposition sensing vectors. In one embodiment, the sensors 14 can bepartially masked to minimize contamination of parameters sensed by thesensors 14.

The size and shape of current delivery electrodes, for bioimpedance, andsensing electrodes can be optimized to maximize sensing performanceAdditionally, the outputs of the sensors 14 can be used to calculate andmonitor blended indices. Examples of the blended indices include but arenot limited to, heart rate (HR) or respiratory rate (RR) response toactivity, HR/RR response to posture change, HR+RR, HR/RR+bioimpedance,and/or minute ventilation/accelerometer and the like.

The sensors 14 can be cycled in order to manage energy, and differentsensors 14 can sample at different times. By way of illustration, andwithout limitation, instead of each sensor 14 being sampled at aphysiologically relevant interval, e.g. every 30 seconds, one sensor 14can be sampled at each interval, and sampling cycles between availablesensors.

By way of illustration, and without limitation, the sensors 14 cansample 5 seconds for every minute for ECG, once a second for anaccelerometer sensor, and 10 seconds for every 5 minutes for impedance.

In one embodiment, a first sensor 14 is a core sensor 14 thatcontinuously monitors and detects, and a second sensor 14 verifies aphysiological status in response to the core sensor 14 raising a flag.Additionally, some sensors 14 can be used for short term tracking, andother sensors 14 used for long term tracking.

The injectable detecting system 12 is inserted into the patient by avariety of means, including but not limited to, catheter delivery, blunttunneling, insertion with a needle, by injection, with a gun or syringedevice with a stiffening wire and stylet and the like. The sensors 14can be inserted in the patient in a non-sterile or sterile setting,non-surgical setting or surgical setting, injected with our withoutanesthesia and injected with or without imaging assistance. Theinjectable detecting system 12 can be anchored in the patient by avariety of means including but not limited to, barbs, anchors, tissueadhesion pads, suture loops.

The injectable detecting system 12 can come in a variety of differentform factors including but not limited to, cylinder, dog-bone, halfdog-bone, trapezoidal cross-section, semicircular cross-section,star-shaped cross-section, v-shaped cross-section, L-shaped, canted, Wshaped, or in other shapes that assist in their percutaneous delivery,S-shaped, sine-wave shaped, J-shaped, any polygonal shape,helical/spiral, fin electrodes, and linear device with a radius ofcurvature to match a radius of the injection site and the like. Further,the injectable detecting system 12 can have flexible bodyconfigurations. Additionally, the injectable detecting system 12 can beconfigured to deactivate selected sensors 14 to reduce redundancy.

The sensors 14 can be made of a variety of materials, including but notlimited to, silicone, polyurethane, Nitinol, a biocompatible material, abioabsorbable material and the like. Electrode sensors 14 can have avariety of different conductors, including but not limited to, platinum,MP35N which is a nickel-cobalt-chromium-molybdenum alloy, MP35N/Ag core,platinum/tantalum core, stainless steel, titanium and the like. Thesensors 14 can have insulative materials, including but not limited to,polyetheretherketone (PEEK), ethylene-tetrafluoroethylene (ETFE),polytetrafluoroethlene (PTFE), polyimide, silicon, polyurethane, and thelike. Further, the sensors 14 can have openings, or an absorbentmaterial, configured to sample a hydration level or electrolyte level ina surrounding tissue site at the location of the sensor 14. The sensor14 electrodes can be made of a variety of materials, including but notlimited to platinum, iridium, titanium, and the like. Electrode coatingscan be included, such as iridium oxide, platinum black, TiN, and thelike.

The injectable detecting system 12 can include one or more arechargeable batteries 36 that can be transcutaneously chargeable withan external unit.

Referring to FIG. 6, in one embodiment, an external device 38, includinga medical treatment device, is coupled to the injectable detectingsystem 12. The external device 38 can be coupled to a monitoring unit 22that is part of the injectable detecting system 12, or in directcommunication with the sensors 14. A variety of different externaldevices 38 can be used, including but not limited to, a weight scale,blood pressure cuff, cardiac rhythm management device, a medicaltreatment device, medicament dispenser, glucose monitor, insulin pump,drug delivery pumps, drug delivery patches, and the like. Suitablecardiac rhythm management devices include but are not limited to, BostonScientific's Latitude system, Medtronic's CareLink system, St. JudeMedical's HouseCall system and the like. Such communication may occurdirectly or via an external translator unit.

The external device 38 can be coupled to an auxiliary input of themonitoring unit 22 at the injectable detecting system 12 or to themonitoring system 22 at the remote monitoring system 18. Additionally,an automated reader can be coupled to an auxiliary input in order toallow a single monitoring unit 22 to be used by multiple patients. Aspreviously mentioned above, the monitoring unit 22 can be at the remotemonitoring system 18 and each patient can have a patient identifier (ID)including a distinct patient identifier. In addition, the ID identifiercan also contain patient specific configuration parameters. Theautomated reader can scan the patient identifier ID and transmit thepatient ID number with a patient data packet such that the main datacollection station can identify the patient.

It will be appreciated that other medical treatment devices can also beused. The injectable detecting system 12 can communicate wirelessly withthe external devices 38 in a variety of ways including but not limitedto, a public or proprietary communication standard and the like. Theinjectable detecting system 12 can be configured to serve as acommunication hub for multiple medical devices, coordinating sensor dataand therapy delivery while transmitting and receiving data from theremote monitoring system 18.

In one embodiment, the injectable detecting system 12 coordinate datasharing between the external systems 38 allowing for sensor integrationacross devices. The coordination of the injectable detecting system 12provides for new pacing, sensing, defibrillation vectors, and the like.

In one embodiment, the processor 20 is included in the monitoring unit22 and the external device 38 is in direct communication with themonitoring unit 22.

In another embodiment, illustrated in FIG. 7, a notification device 42is coupled to the injectable detecting system 12 and the remotemonitoring system 18. The notification device 42 is configured toprovide notification when values received from the sensors 14 are notwithin acceptable physiological ranges. The notification device 42 canbe at the remote monitoring system 18 or at the monitoring unit 22 thatis part of the injectable detecting system 12. A variety of notificationdevices 42 can be utilized, including but not limited to, a visiblepatient indicator, an audible alarm, an emergency medical servicenotification, a call center alert, direct medical provider notificationand the like. The notification device 42 provides notification to avariety of different entities, including but not limited to, thepatient, a caregiver, the remote monitoring system, a spouse, a familymember, a medical provider, from one device to another device such asthe external device 38, and the like.

Notification can be according to a preset hierarchy. By way ofillustration, and without limitation, the preset hierarchy can be,patient notification first and medical provider second, patientnotification second and medical provider first, and the like. Uponreceipt of a notification, a medical provider, the remote monitoringsystem 18, or a medical treatment device can trigger a high-ratesampling of physiological parameters for alert verification.

The system 10 can also include an alarm 46, that can be coupled to thenotification device 42, for generating a human perceptible signal whenvalues received from the sensors 14 are not within acceptablephysiological ranges. The alarm 46 can trigger an event to rendermedical assistance to the patient, provide notification as set forthabove, continue to monitor, wait and see, and the like.

When the values received from the sensors 14 are not within acceptablephysiological ranges the notification is with the at least one of, thepatient, a spouse, a family member, a caregiver, a medical provider andfrom one device to another device, to allow for therapeutic interventionto prevent decompensation.

In another embodiment, the injectable detecting system 12 can switchbetween different modes, wherein the modes are selected from at leastone of, a stand alone mode with communication directly with the remotemonitoring system 18, communication with an implanted device,communication with a single implanted device, coordination betweendifferent devices (external systems) coupled to the plurality of sensorsand different device communication protocols.

By way of illustration, and without limitation, the patient can be acongestive heart failure patient. Heart failure status is determined bya weighted combination change in sensor outputs and be determined by anumber of different means, including but not limited to, (i) when a rateof change of at least two sensor outputs is an abrupt change in thesensor outputs as compared to a change in the sensor outputs over alonger period of time, (ii) by a tiered combination of at least a firstand a second sensor output, with the first sensor output indicating aproblem that is then verified by at least a second sensor output, (iii)by a variance from a baseline value of sensor outputs, and the like. Thebaseline values can be defined in a look up table.

In another embodiment, heart failure status is determined using three ormore sensors by at least one of, (i) when the first sensor output is ata value that is sufficiently different from a baseline value, and atleast one of the second and third sensor outputs is at a value alsosufficiently different from a baseline value to indicate heart failurestatus, (ii) by time weighting the outputs of the first, second andthird sensors, and the time weighting indicates a recent event that isindicative of the heart failure status and the like.

In one embodiment, the wireless communication device 16 can include a,modem, a controller to control data supplied by the injectable detectingsystem 12, serial interface, LAN or equivalent network connection and awireless transmitter. Additionally, the wireless communication device 16can include a receiver and a transmitter for receiving data indicatingthe values of the physiological event detected by the plurality ofsensors, and for communicating the data to the remote monitoring system18. Further, the wireless communication device 16 can have data storagefor recording the data received from the injectable detecting system 12and an access device for enabling access to information recording in thedata storage from the remote monitoring system 18.

In various embodiments, the remote monitoring system 18 can include a,receiver, a transmitter and a display for displaying data representativeof values of the one physiological event detected by the injectabledetecting system 12. The remote monitoring system can also include a,data storage mechanism that has acceptable ranges for physiologicalvalues stored therein, a comparator for comparing the data received fromthe injectable detecting system 12 with the acceptable ranges stored inthe data storage device and a portable computer. The remote monitoringsystem 18 can be a portable unit with a display screen and a data entrydevice for communicating with the wireless communication device 16.

Referring now to FIG. 8, for each sensor 14, a sensor lead 112 and 114conveys signals from the sensor 14 to the monitoring unit 22 at theinjectable detecting system 12, or through the wireless communicationdevice 16 to the remote monitoring system 18.

In one embodiment, each signal from a sensor 14 is first passed througha low-pass filter 116, at the injectable detecting system 12 or at theremote monitoring system 18, to smooth the signal and reduce noise. Thesignal is then transmitted to an analog-to-digital converter 118A, whichtransforms the signals into a stream of digital data values that can bestored in a digital memory 118B. From the digital memory 118B, datavalues are transmitted to a data bus 120, along which they aretransmitted to other components of the circuitry to be processed andarchived. From the data bus 120, the digital data can be stored in anon-volatile data archive memory. The digital data can be transferredvia the data bus 120 to the processor 20, which processes the data basedin part on algorithms and other data stored in a non-volatile programmemory.

The injectable detecting system 12 can also include a power managementmodule 122 configured to power down certain components of the system,including but not limited to, the analog-to-digital converters 118A and124, digital memories 118B and the non-volatile data archive memory andthe like, between times when these components are in use. This helps toconserve battery power and thereby extend the useful life. Othercircuitry and signaling modes may be devised by one skilled in the art.

As can be seen in FIG. 9, a control unit 126 is included at thedetecting system 12, the remote monitoring system 18, or at bothlocations.

In one embodiment, the control unit 126 can be a microprocessor, forexample, a Pentium or 486 processor. The control unit 126 can be coupledto the sensors 14 directly at the injectable detecting system 12,indirectly at the injectable detecting system 12 or indirectly at theremote monitoring system 18. Additionally the control unit 126 can becoupled to one or more devices, for example, a blood pressure monitor,cardiac rhythm management device, scale, a device that dispensesmedication, a device that can indicate the medication has beendispensed, and the like.

The control unit 126 can be powered by AC inputs which are coupled tointernal AC/DC converters 134 that generate multiple DC voltage levels.After the control unit 126 has collected the patient data from thesensors 14, the control unit 126 encodes the recorded patient data andtransmits the patient data through the wireless communication device 16to transmit the encoded patient data to a wireless network storage unit128 at the remote monitoring system 18, as shown in FIG. 10. In anotherembodiment, wireless communication device 16 transmits the patient datafrom the injectable detecting system 12 to the control unit 126 when itis at the remote monitoring system 18.

Every time the control unit 126 plans to transmit patient data to a maindata collection station 130, located at the remote monitoring system 18,the control unit 126 attempts to establish a communication link. Thecommunication link can be wireless, wired, or a combination of wirelessand wired for redundancy, e.g., the wired link checks to see if awireless communication can be established. If the wireless communicationlink 16 is available, the control unit 126 transmits the encoded patientdata through the wireless communication device 16. However, if thewireless communication device 16 is not available for any reason, thecontrol unit 126 waits and tries again until a link is established.

Referring now to FIG. 11, one embodiment of an internal structure of amain data collection station 130, at the remote monitoring system 18, isillustrated. The patient data can be transmitted by the remotemonitoring system 18 by either the wireless communication device 16 orconventional modem to the wireless network storage unit 128. Afterreceiving the patient data, the wireless network storage unit 128 can beaccessed by the main data collection station 130. The main datacollection station 130 allows the remote monitoring system 18 to monitorthe patient data of numerous patients from a centralized locationwithout requiring the patient or a medical provider to physicallyinteract with each other.

The main data collection station 130 can include a communications server136 that communicates with the wireless network storage unit 128. Thewireless network storage unit 128 can be a centralized computer serverthat includes a unique, password protected mailbox assigned to andaccessible by the main data collection station 130. The main datacollection station 130 contacts the wireless network storage unit 128and downloads the patient data stored in a mailbox assigned to the maindata collection station 130.

Once the communications server 136 has formed a link with the wirelessnetwork storage unit 128, and has downloaded the patient data, thepatient data can be transferred to a database server 138. The databaseserver 138 includes a patient database 140 that records and stores thepatient data of the patients based upon identification included in thedata packets sent by each of the monitoring units 22. For example, eachdata packet can include an identifier.

Each data packet transferred from the remote monitoring system 18 to themain data collection station 130 does not have to include any patientidentifiable information. Instead, the data packet can include theserial number assigned to the specific injectable detecting system 12.The serial number associated with the detecting system 12 can then becorrelated to a specific patient by using information stored on thepatient database 138. In this manner, the data packets transferredthrough the wireless network storage unit 128 do not include anypatient-specific identification. Therefore, if the data packets areintercepted or improperly routed, patient confidentiality can not bebreached.

The database server 138 can be accessible by an application server 142.The application server 142 can include a data adapter 144 that formatsthe patient data information into a form that can be viewed over aconventional web-based connection. The transformed data from the dataadapter 144 can be accessible by propriety application software througha web server 146 such that the data can be viewed by a workstation 148.The workstation 148 can be a conventional personal computer that canaccess the patient data using proprietary software applications through,for example, HTTP protocol, and the like.

The main data collection station further can include an escalationserver 150 that communicates with the database server 138. Theescalation server 150 monitors the patient data packets that arereceived by the database server 138 from the monitoring unit 22.Specifically, the escalation server 150 can periodically poll thedatabase server 138 for unacknowledged patient data packets. The patientdata packets are sent to the remote monitoring system 18 where theprocessing of patient data occurs. The remote monitoring system 18communicates with a medical provider in the event that an alert isrequired. If data packets are not acknowledged by the remote monitoringsystem 18. The escalation server 150 can be programmed to automaticallydeliver alerts to a specific medical provider if an alarm message hasnot been acknowledged within a selected time period after receipt of thedata packet.

The escalation server 150 can be configured to generate the notificationmessage to different people by different modes of communication afterdifferent delay periods and during different time periods.

The main data collection station 130 can include a batch server 152connected to the database server 138. The batch server 152 allows anadministration server 154 to have access to the patient data stored inthe patient database 140. The administration server 154 allows forcentralized management of patient information and patientclassifications.

The administration server 154 can include a batch server 156 thatcommunicates with the batch server 152 and provides the downloaded datato a data warehouse server 158. The data warehouse server 158 caninclude a large database 160 that records and stores the patient data.

The administration server 154 can further include an application server162 and a maintenance workstation 164 that allow personnel from anadministrator to access and monitor the data stored in the database 160.

The data packet utilized in the transmission of the patient data can bea variable length ASCII character packet, or any generic data formats,in which the various patient data measurements are placed in a specificsequence with the specific readings separated by commas The control unit126 can convert the readings from each sensor 14 into a standardizedsequence that forms part of the patient data packet. In this manner, thecontrol unit 126 can be programmed to convert the patient data readingsfrom the sensors 14 into a standardized data packet that can beinterpreted and displayed by the main data collection station 130 at theremote monitoring system 18.

Referring now to the flow chart of FIG. 12, if an external device 38fails to generate a valid reading, as illustrated in step A, the controlunit 126 fills the portion of the patient data packet associated withthe external device 38 with a null indicator. The null indicator can bethe lack of any characters between commas in the patient data packet.The lack of characters in the patient data packet can indicate that thepatient was not available for the patient data recording. The nullindicator in the patient data packet can be interpreted by the main datacollection station 130 at the remote monitoring system 18 as a failedattempt to record the patient data due to the unavailability of thepatient, a malfunction in one or more of the sensors 14, or amalfunction in one of the external devices 38. The null indicatorreceived by the main data collection station 130 can indicate that thetransmission from the injectable detecting system 12 to the remotemonitoring system 18 was successful. In one embodiment, the integrity ofthe data packet received by the main data collection station 130 can bedetermined using a cyclic redundancy code, CRC-16, check sum algorithm.The check sum algorithm can be applied to the data when the message canbe sent and then again to the received message.

After the patient data measurements are complete, the control unit 126displays the sensor data, including but not limited to blood pressurecuff data and the like, as illustrated by step B. In addition todisplaying this data, the patient data can be placed in the patient datapacket, as illustrated in step C.

As previously described, the system 10 can take additional measurementsutilizing one or more auxiliary or external devices 38 such as thosementioned previously. Since the patient data packet has a variablelength, the auxiliary device patient information can be added to thepatient data packet being compiled by the remote monitoring unit 22during patient data acquisition period being described. Data from theexternal devices 38 is transmitted by the wireless communication device16 to the remote monitoring system 18 and can be included in the patientdata packet.

If the remote monitoring system 18 can be set in either the auto mode orthe wireless only mode, the remote monitoring unit 22 can firstdetermine if there can be an internal communication error, asillustrated in step D.

A no communication error can be noted as illustrated in step E. If acommunication error is noted the control unit 126 can proceed towireless communication device 16 or to a conventional modem transmissionsequence, as will be described below. However, if the communicationdevice is working, the control unit 126 can transmit the patient datainformation over the wireless network 16, as illustrated in step F.After the communication device has transmitted the data packet, thecontrol unit 126 determines whether the transmission was successful, asillustrated in step G. If the transmission has been unsuccessful onlyonce, the control unit 126 retries the transmission. However, if thecommunication device has failed twice, as illustrated in step H, thecontrol unit 126 proceeds to the conventional modem process if theremote monitoring unit 22 was configured in an auto mode.

When the control unit 126 is at the injectable detecting system 12, andthe control unit 126 transmits the patient data over the wirelesscommunication device 16, as illustrated in step I, if the transmissionhas been successful, the display of the remote monitoring unit 22 candisplay a successful message, as illustrated in step J. However, if thecontrol unit 126 determines in step K that the communication of patientdata has failed, the control unit 126 repeats the transmission until thecontrol unit 126 either successfully completes the transmission ordetermines that the transmission has failed a selected number of times,as illustrated in step L. The control unit 126 can time out the and afailure message can be displayed, as illustrated in steps M and N. Oncethe transmission sequence has either failed or successfully transmittedthe data to the main data collection station, the control unit 126returns to a start program step O.

As discussed previously, the patient data packets are first sent andstored in the wireless network storage unit 128. From there, the patientdata packets are downloaded into the main data collection station 130.The main data collection station 130 decodes the encoded patient datapackets and records the patient data in the patient database 140. Thepatient database 140 can be divided into individual storage locationsfor each patient such that the main data collection station 130 canstore and compile patient data information from a plurality ofindividual patients.

A report on the patient's status can be accessed by a medical providerthrough a medical provider workstation that is coupled to the remotemonitoring system 18. Unauthorized access to the patient database can beprevented by individual medical provider usernames and passwords toprovide additional security for the patient's recorded patient data.

The main data collection station 130 and the series of work stations 148allow the remote monitoring system 18 to monitor the daily patient datameasurements taken by a plurality of patients reporting patient data tothe single main data collection station 130. The main data collectionstation 130 can be configured to display multiple patients on thedisplay of the workstations 148. The internal programming for the maindata collection station 130 can operate such that the patients areplaced in a sequential top-to-bottom order based upon whether or not thepatient can be generating an alarm signal for one of the patient databeing monitored. For example, if one of the patients monitored bymonitoring system 130 has a blood pressure exceeding a predeterminedmaximum amount, this patient can be moved toward the top of the list ofpatients and the patient's name and/or patient data can be highlightedsuch that the medical personnel can quickly identify those patients whomay be in need of medical assistance. By way of illustration, andwithout limitation, the following paragraphs is a representative orderranking method for determining the order which the monitored patientsare displayed:

Alarm Display Order Patient Status Patients are then sorted 1 MedicalAlarm Most alarms violated to least alarms violated, then oldest tonewest 2 Missing Data Alarm Oldest to newest 3 Late Oldest to newest 4Reviewed Medical Alarms Oldest to newest 5 Reviewed Missing Data Oldestto newest Alarms 6 Reviewed Null Oldest to newest 7 NDR Oldest to newest8 Reviewed NDR Oldest to newest

As listed in the above, the order of patients listed on the display canbe ranked based upon the seriousness and number of alarms that areregistered based upon the latest patient data information. For example,if the blood pressure of a single patient exceeds the tolerance leveland the patient's heart rate also exceeds the maximum level, thispatient will be placed above a patient who only has one alarm condition.In this manner, the medical provider can quickly determine which patientmost urgently needs medical attention by simply identifying thepatient's name at the top of the patient list. The order which thepatients are displayed can be configurable by the remote monitoringsystem 18 depending on various preferences.

As discussed previously, the escalation server 150 automaticallygenerates a notification message to a specified medical provider forunacknowledged data packets based on user specified parameters.

In addition to displaying the current patient data for the numerouspatients being monitored, the software of the main data collectionstation 130 allows the medical provider to trend the patient data over anumber of prior measurements in order to monitor the progress of aparticular patient. In addition, the software allows the medicalprovider to determine whether or not a patient has been successful inrecording their patient data as well as monitor the questions beingasked by the remote monitoring unit 22.

As previously mentioned, the system 10 uses an intelligent combinationof sensors to enhance detection and prediction capabilities.Electrocardiogram circuitry can be coupled to the sensors 14, orelectrodes, to measure an electrocardiogram signal of the patient. Anaccelerometer can be mechanically coupled, for example adhered oraffixed, to the sensors 14, adherent patch and the like, to generate anaccelerometer signal in response to at least one of an activity or aposition of the patient. The accelerometer signals improve patientdiagnosis, and can be especially useful when used with other signals,such as electrocardiogram signals and impedance signals, including butnot limited to, hydration respiration, and the like. Mechanicallycoupling the accelerometer to the sensors 14, electrodes, for measuringimpedance, hydration and the like can improve the quality and/orusefulness of the impedance and/or electrocardiogram signals. By way ofillustration, and without limitation, mechanical coupling of theaccelerometer to the sensors 14, electrodes, and to the skin of thepatient can improve the reliability, quality and/or accuracy of theaccelerometer measurements, as the sensor 14, electrode, signals canindicate the quality of mechanical coupling of the patch to the patientso as to indicate that the device is connected to the patient and thatthe accelerometer signals are valid. Other examples of sensorinteraction include but are not limited to, (i) orthopnea measurementwhere the breathing rate is correlated with posture during sleep, anddetection of orthopnea, (ii) a blended activity sensor using therespiratory rate to exclude high activity levels caused by vibration(e.g. driving on a bumpy road) rather than exercise or extreme physicalactivity, (iii) sharing common power, logic and memory for sensors,electrodes, and the like.

FIG. 13 shows one embodiment of an injection system 200 for use withmultiple injectable detecting systems 12 that includes a body having amagazine 205 with several injectable detecting systems 12 loadedtherein. A needle portion of the injection system 200 can be placedagainst the tissue 210, as shown. A handle 215 can be pulled proximally220 and a pusher is advanced to inject one of the injectable detectingsystems 12 out of the needle end into the patient 40, and injectabledetecting systems 12 in the magazine 205 are advanced such that the nextinjectable detecting system 12 is ready for injection at a subsequentlocation.

FIG. 14 shows one embodiment of an injection system 250 that includes abody with a needle 255 configured to hold one or more injectabledetecting systems 12. The needled 255 includes a bevel needle shaped tip265, that is inserted into the tissue with the injectable detectingsystem 12 loaded into the needle 255. A pusher 265 is advanced distallyin the body to advance the injectable detecting system 12 into thetissue after the needle tip has penetrated the tissue

While the invention is susceptible to various modifications andalternative constructions, certain illustrated embodiments thereof areshown in the drawings and have been described above in detail. It shouldbe understood, however, that there is no intention to limit theinvention to the specific form or forms disclosed, but on the contrary,the intention is to cover all modifications, alternative constructions,and equivalents falling within the spirit and scope of the invention.

The invention claimed is:
 1. An injectable device for use in subcutaneous physiological monitoring of a patient, the injectable device comprising: a body; a plurality of sensors that provide an indication of at least one physiological event of a patient, wherein the plurality of sensors include current delivery electrodes and sensing electrodes in contact with tissue of the patient and spaced along the body of the injectable device; and a monitoring unit located within the body and coupled to the plurality of sensors and configured to monitor a bioimpedance of the patient using the current delivery electrodes and sensing electrodes, wherein the monitoring unit utilizes the monitored bioimpedance to determine a hydration of surrounding tissue and wherein the monitoring unit is further configured to, based at least in part on the determined hydration, detect an impending cardiac decompensation of the patient.
 2. The injectable device of claim 1, further including electrocardiogram circuitry coupled to the two or more electrodes to measure an electrocardio gram signal of the patient.
 3. The injectable device of claim 2, wherein the monitoring unit utilizes the measured impedance signal to monitor a respiration signal associated with the patient.
 4. The injectable device of claim 3, wherein the monitoring unit compares the monitored hydration, the respiration signal and the electrocardiogram signal to baseline values established for each, wherein the monitoring unit sets a flag indicating cardiac decompensation based on a combination of the compared values.
 5. The injectable device of claim 1, further including an accelerometer located within the body that generates an activity signal in response to at least one of a activity or a position of the patient.
 6. The injectable device of claim 5, wherein the accelerometer is a three-axis accelorometer configured to measure at least one inclincation, a position, an orientation, and an acceleration of the patient in three dimensions.
 7. The injectable device of claim 5, wherein the accelerometer is comprised of at least one of a piezoelectric accelerometer, a capacitive accelerometer, or an electromechanical accelerometer.
 8. The injectable device of claim 5, wherein the monitoring unit utilizes activity data received from the accelerometer to detect physiological events and identify patient states when data collection is desirable.
 9. The injectable device of claim 8, wherein patient states in which data collection is desirable include rest states.
 10. The injectable device of claim 1, wherein the body has a proximal end and a distal end, wherein the distal end is shaped to penetrate tissue.
 11. The injectable device of claim 1, wherein the injectable device can be inserted in the patient in one or more of a non-sterile setting, sterile setting, non-surgical setting, and surgical setting.
 12. An injectable device for use in subcutaneous physiological monitoring of a patient, the injectable device comprising: a hermetically sealed body; a plurality of sensors that provide an indication of at least one physiological event of a patient, wherein the plurality of sensors includes an accelerometer located within the body that generates an activity signal in response to at least one of a activity or a position of the patient and at least two electrodes spaced along the hermetically sealed body of the injectable device and in contact with tissue of the patient for monitoring a physiological signal associated with the patient; and a monitoring unit located within the body and coupled to the accelerometer and the at least two electrodes, wherein the at least two electrodes are utilized to measure an impedance signal related, wherein the monitoring unit utilizes the measured impedance to determine a hydration of surrounding tissue of the patient and wherein the monitoring unit is further configured to, based at least in part on the determined hydration and the activity level of the patient, detect an impending cardiac decompensation of the patient.
 13. The injectable device of claim 12, wherein the accelerometer is a three-axis accelorometer configured to measure at least one inclincation, a position, an orientation, and an acceleration of the patient in three dimensions.
 14. The injectable device of claim 12, wherein the monitoring unit utilizes the monitored activity level of the patient to identify patient states when data collection is appropriate.
 15. The injectable device of claim 14, wherein patient states in which data collection is appropriate includes rest states.
 16. The injectable device of claim 12, further including electrocardiogram circuitry coupled to the two or more electrodes to measure an electrocardiogram signal of the patient.
 17. The injectable device of claim 16, wherein the monitoring unit utilizes the measured impedance signal to monitor a respiration signal associated with the patient.
 18. The injectable device of claim 16, wherein the monitoring unit compares the monitored hydration, the respiration signal and the electrocardiogram signal to baseline values established for each, wherein the monitoring unit sets a flag indicating cardiac decompensation based on a combination of the compared values. 